String trimmers typically feature two-cycle gasoline engines for power. A string trimmer's engine turns the trimmer head, which has the cutting line attached by a flexible metal driveshaft. The shaft runs down the length of driveshaft housing, to which the engine and trimmer head are attached. As the driveshaft is a moving part, it is necessary that it be properly lubricated. Periodical inspection and lubrication of the shaft will help maintain the trimmer in proper working order.
Place the string trimmer on a convenient work surface. Pull the spark plug wire from the spark plug to prevent accidental starting.
Locate the gearbox on the end of the aluminium driveshaft housing just above the trimmer head. Loosen and remove the screws holding the gearbox to the shaft housing with a screwdriver.
Remove the gearbox and attached trimmer head from the shaft housing.
Pull the flex driveshaft from the shaft housing.
Wipe down the flex driveshaft with a rag. Remove as much of the old grease and any dirt or debris as possible. Wear a pair of gloves for hand protection.
Apply a thin coat of shaft lubricant to the entire length of the flex driveshaft. Use a rag, if necessary, to help apply the lubricant.
Insert the flex driveshaft back into the shaft housing. Slide the gearbox back onto the shaft housing and secure it with the screws that you previously removed.